Charles e



(iNo Model.)

C. E. SCRIBNER.A

APPARATUS POR TELEPHONE SWITGHBOARDS.

No. 563,073. Y Patented Jun 30, 1896.

UNITED STATES PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR T0 Tl-IE IVESTERNELECTRIC COMPANY, OF SAME PLACE.

APPARATUS FOR TELEPHONE-SWITCHBOARDS.

SPECIFICATION forming part of Letters Patent N0. 563,073, dated June 30,1896.

Application led .Tune l2, 1895. Serial No. 552,525. (No model.)

To all whom t may concern,.- connection is made with the line andsubsti- Be it known that I, CHARLES E. SCRIBNER, tuting for it asupervisory signal-lampassoa citizen of the United States, residing atChiciated with the connecting-plu g, and for causcago, in the county ofCook and State of Illiing the illumination of the latter signal-lamp 555 nois, have invented acertain new and useful When the telephone isreplaced upon its Improvement in Apparatus for Telephoneswitch-hook atthe substation. Switchboards, (Case No. 384,) of which the Eachtelephone-line is controlled at its subfolloiving is a full, clear7concise, and exact station by a switch operated automaticallydescription, reference being had to the acin the use of thetelephone,whichis arranged 6o 1o companying drawing, forming a part ofthis to ,close the line-circuit While the telephone specification. is inuse, but to interrupt this connection, or

My invention relates to the automatic opt0 close it through a path ofvery high reeration of signals of telephone-lines termisistance, whenthe telephone is idle. At the nating in a telephone-switchboard. Itsobcentral station I lead from one conductor of 65 15 ject is, ingeneral, to provide for the switchthe line-circuit a ground branchthrough an board-operator a simple and efficient system impedance-coiland the line-signal lamp, inof signals adapted to indicate continuouslycluding a signaling-battery which may be the condition of eachtelephone-line, Vor of common to different lines of the exchange. thedifferent members of a pair of connected When the switch at thesubstation is oper- 7o 2o lines. ated in the use of the telephone, theline-sig- Prior to my invention annunciators or visinal is illuminatedand indicates the call or ble signals have been included intelephoneinitial signal to the attendant. lines, together With sourcesof signaling-cur- Each terminal plug is provided with a closed rent, thetelephone-lines being provided with circuit through one helix of aninduction-coil, 7 5 2 5 switches at their substations adapted to openthe other helix of the same coil being included and close theline-circuit, and thus to disin the circuit of the other terminal plugot play or render inert the signaling instruthe pair, and from thecentral point of each ments at the central station when the telehelixaconductor is led through asupervisory phone is in use or is idle. Whensuch lines lamp-signal to the free pole of the same sig- 8o 3o wereconnected together by means of loopnaling-battery. Thesehelices areconstructed conductors in the switchboard, it has been of such lowresistance that When a plug is infurther customary to place inconnection serted into a spring-jack the line-signal lamp, With severedportions of the link conductors being shunted by the induction-coilhelix of other visible signals associated with the terlow resistance, isextinguished; In a shunt 8 5 minal plugs of the plug-circuit, designedto about the supervisory signal is connected a enable the operator tosupervise the connecresistance-coil, together with a' battery or tionduring its continuance by indicating the other source of current of suchpolarity and condition of the telephonie appliances at both strengththat the current from the common stations of the united-circuits.signaling-battery, in the closed line-circuit, 9o 4o In a priorapplication, iiled April 16, 1895, is diverted from the signal-lamp, or,in other Serial No. 545,855, I have disclosed a mode Words, the batteryin circuit about the superof using small incandescent lamps as suchvisory signal coperates with the main sigvisible signals in telephonecircuits. naling-battery to produce a condition of no My presentinvention aims to employ such dierence of potential between theterminals 95 45 signal-lamps, placed in direct connection of the lamp.Under this condition, when the with the telephone-line, for indicatingthe circuit at the substation is again interrupted, various signalsrequired; and to this end it this balanced relation is destroyed andcurcomprises means for exciting a line-signal rent is created throughthe supervisory sigpermanently associated with the line, when nal tocause its illumination. The operation roo 5o the telephone is removedfrom the switchof this system of signaling is then as folliookforextinguishing this signal-lamp when lows: When the telephone at thesubstation is removed from its switch-hook, to transmit an initial orcall signal, the line-lamp is illuminated. When the operator makesconnection with the line, this lamp is extinguished. Then the telephoneis returned to its idle position, the supervisory signal isilluniinated. Since both members of the pair of plugs used in unitingtwo lines are provided with such supervisory signals, these signalsconstantly indicate to the attendant the condition of the substationapparatus at both stations. The operator may be instructed to remove theconnection only when both supervisory signals have become lighted.

For the purpose of rendering the lamp-signals as sensitive as possibleto current in the line-circuit, I prefer to employ a device described ina pending application led April I6, 1895, Serial No. 545,856, whichconsists in a shunt-circuit including a source of current about thesignal-lamp, the current in this circuit being so adjusted with relationto the lamp as to be barely insufiicient to illuminate the lamp. A veryslight addition to this current, by an independent current created inthe complete signaling-circuit, is suiiicient to cause the fullillumination of the lamp, and thus to display the signal.

My invention is adapted for use in exchange systems in which thesubstation-transmitters are supplied with current from a common sourcelocated at the central station. I have illustrated it in connection withsuch a system in the accompanying drawing.

In the drawing two substations are represented connected bylineconductors with the apparatus of a telephone-switchboard at a centralstation. The appliances at the substations are of the usual character.They comprise a receiving-telephone a, a transmitting-telephone d', asignal-bell a2, and an automatically operated switch a3, acting toswitch the telephone and the bell alternately in to connection with theline. The bell a2 should have a high resistance, compared to that of thetelephonewas iive thousand ohmsfor the purpose of practicallyinterrupting the line-circuit when the telephone branch is linterrupted. Two substations thus equipped,

B and C, are shown in the drawing. Station B is connected by lineconductors l and 2 with apparatus in a switchboard at the centralstat-ion D, the different line conductors terminating in thecorresponding contactpieces of a spring-jack e in the switchboard. Theline conductor l is continued through an inductive resistance orimpedance coil f, and through the line-signal lamp g to one pole of abattery or other source ot current lL, which is common to the differentlines of the exchange. The other line conductor 2 is continued through asimilar impedance-coil 1l to the other pole of the same battery h. Theimpedance-.coils fand@l should be of about one hundred ohms resistanceeach. A conductor 3, including a resistance-coil k, is connected inshunt of the signal-lamp g, and includes in its circuit a battery orother source of current 7i', which also is common to the differentlines. The strength of battery 71. and the resistance of coil la are soadjusted that sufficient current fiows through lamp g to raise it almostto the point of illumination.

The usual pairs of connecting-plugs Z and Z are provided for theoperator to enable her to establish connection between differentspring-jacks for the purpose of looping lines into circuit with eachother. The like contact-pieces of these loop-plugs are connectedtogether, the tips m being united through a conductor 4, and the sleevesor tubes through another conductor 5. The switch springs and the normalresting-contacts of a callingkey 1L are included in these conductors,the key being adapted, when operated, to disconnect the plug Z from itsmate and to close its terminals to the poles of a generator o, suitablefor operating the substation-bells a2. A listenin g-key p also has itssprings connected with the conductors 4 and 5, its oilice being tobridge the operators telephone-set q across the plug-circuit 4 5 whenthe key is depressed.

The conductor 5 includes in series two helices r and r2 of a transformeror inductioncoil 7'. From the point of junction of these two helices aconductor 6 is led to that pole of the battery 7L which is connectedwith line conductors 2. The conductor 4 of the plugcircuit likewiseincludes in series two helices r3 r4 of the same induction-coil. Thesehelices are united through two signal-lamps s and s. These lamps areassociated, respectively, with the terminal plugs l and Z oftheplug-circuit, and should for convenience be placed close together inthe switchboard.

The point of junction of lamps s and s is connected with a battery t,whose other terminal is connected through a conductor 7 with that poleof battery h in which t-he line conductors l terminate. A shunt-circuitis provided about each of the lamps s and s', as about the line-lamps.This shunt consists in a resistance-coil, connected from one terminal ofthe lamp to the conductor 7, the resistance-coils about lamps s and sbeing designated u and u', respectively. The lamp s is thus in a closedcircuit formed by the resistance-coil u and battery i. The lamp s is ina similar circuit with the battery t and its coil u. The direction andstrength of battcryzf in each of these circuits should be so adjustedwith relation to the resistance-coil that while the plug-circuit is openor disconnected a sufficient current will traverse each of the lamps sand s to fully illuminate them; but its strength should also be soadjusted with relation to battery h that when the conductors 4 and 5 ofthe plug-circuit are connected with the conductors l and 2 of theline-circuit, the latter being connected together through alow-resistance path at the substation, sufficient current from battery twill be diverted from its path through lamp-signals IOO IIO

S and s' to leave these unilluminated. This adjustment will be referredto later in connection with the operation of the complete system.

It may be sufficient here to state that good results may be obtainedwith a battery h of forty volts electromotive force, and a battery t ofsix volts, the resistance of coils u and u' being approximately fifteenohms, and that of the substation-telephone being about one hundred ohms.Like poles of batteries 7L and tshould be connected with conductor 7.The helices of induction-coil r should be of moderately-lowresistance-for example, of about twenty-ve ohms each.

ln order to trace the operation of this system, assume that subscriberat station B requires a connection with station C. The subscriber at theformer station, by removing his receiving-telephone a from hisswitch-hook, permits the latter to connect the line conductors throughthe low-resistance telephoneset. The battery h now finds circuit throughthe line conductors l and 2 and this low-resistance branch at thesubstation. This current is ot course divided in the switchboard betweenconductors l and 3, the greater part, however, traversing conductor land the lamp-signal g. A sufficient current is thus caused to flowthrough this signal-lamp, in addition to that normally iiowing frombattery h', to illuminate the lamp and thus to indicate to the attendantthe subscribers initial signal. The operator then inserts plugZ intospring-jack e, and, by operating her listening-liey p, brings hertelephone-set q into connection with the plug-circuit, and learns theorder from the subscriber for the connection desired. By the insertionof this plug into spring-jack e, the helices r and r3 of induction-coilr are brought into shunt of the impedance-coil t', and theimpedance-coilf and line-lamp g, respectively, so that the currentproduced by battery h through signallamp gis diverted from that paththrough the path of low resistance formed by conductor 7, lamp s, a coilu, and battery in parallel,

' helix r3 and conductor 4, returning through conductor 5, helix r', andwire 6.l The signal-lamp g is thus extinguished or returned to itsnormal inert condition.

It will be noted that during the idleness of the plug-circuit thebatteryt creates in the circuit formed by resistance-coil u, lamp s,

- and its leads a current which fully illuminates the supervisory signals. Vhen the plug is inserted in the spring-jack e, however, a portion ofthe current from battery 2f is diverted through the line-circuit; or, inother words, batteries 7L and t cooperate to produce a condition of nodifference of potential between the terminals of the signal .3,practically the entire current created by the two batteries findingcircuit through the resistancecoil u to the conductor 4 and thence tothe telephone-line. The current from battery h nds circuit throughconductor 7, from whose point of junction with the other circuits it hastwo paths, namely, one through battery t and each of the lamps s and s'to the portions 4 4 of the conductor of the plug circuit and thence tothe corresponding lines, and the other through resistance-coils a and uto the same portions of the conductor of the plugcircuit. Consideringthe circuit to the callingline, for instance, the current has a paththrough a circuit of two branches, one including coil u and the otherincluding lamp s and battery t. In the latter circuit the opposingelectromotive force of battery t is so adjusted with relation to theresistance of coil u and the current which is passing through it frombattery hV that the current tending to flow from battery h through thelamp s is exactly opposed; while as to the current which battery t tendsto set up in the short closed circuit including coil u, lamp s, andbattery that is opposed by the difference of potential between theterminals of coil fa, which is set up by the battery h. To be accurate,the electromotive force of battery t, the resistance of coil u, theresistance of the external circuit through the line, and theelectro'motive force of battery h are so adjusted with relation to eachother that no difference of potential exists between the terminals ofthe lamp. The supervisory signals is thus extinguished, and remains darkas long as this condition of balance is maintained by the continuity ofthe line-circuit at the substation.

Having learned the order, the operator establishes connection with thelines S 9 to station C by inserting plug Z' into spring-jack e of thatline. She rings the substation-bell a2 at station C by operating thecalling-key n in the usual way.

When the plug Z is inserted into the springjack e, no current is createdby battery h through the plug Z', since the line-circuit at station C isas yet interrupted, or is at least closed only through the bell a2 ofvery high resistance. Hence supervisory signal s' is lighted. Thiscondition remains until the subscriber at station C, responding to thesignal of his bell, removes his telephone from its switch-hook andpermits the latterv to close the lin e-circuit through the telephone.When this is done, current finds circuit from battery h, throughconductor 7 and resistancecoil u, thence through conductor 4, plug l',to the line-circuit, returning through the corresponding conductors ofthe other side of the circuit. This current is in the proper directionand of the proper strength to bring about the condition of no differenceof potential between the terminals of signal s', so that the latter alsobecomes dark. When both supervisory signals are thus obscured, it may beassumed that the subscribers are in conversation. If either telephone bereplaced upon its switch-hook,the current in that line-circuit isinterrupted and the corresponding supervisory signal is illuminated.When both signals become lighted, it may be assumed that IIO circuitsand sources of current which con-.

stitutes my invention is not limited to use with lamp-signals, since anyof several wellknown forms of visible signals might be substituted forthe signal-lamps described. It is also possible to adaptthe same circuitarrangement to systems involving other modes of supplying current to thesubstation-transmitter without the exercise of invention.

I claim as new- 1. The combination with a signaling-circuit divided atVone point Yinto two parallel branches of fixed resistance, of means forvarying the resistance of the signaling-circuit, a source ofsignaling-current in the-undivided portion of the Vsignaling-circuit, asignal-indicating instrument requiring for its operation a denitepredetermined current in one oi' the branches, a separate source ofcurrent in one of the parallel branches, the polarivties of the sourceof signaling-current and of the said other source being oppositelydirected Vin the portion of the circuit including the signalinginstrument, the electro- -motive force of said last-mentioned sourcebeing sufficient to prevent current from-actuating the signal whenthesignaling-circuit is closed;V whereby the closing of thesignalingcircuit renders the signal inert, and the opening of thesignaling-circuit causes its display, substantially as described.

2. The combination with a telephone-line provided with a switch adaptedto interrupt the circuit and a source of current in the line, a portionof the line being divided into two parallel branches, of a signal-lampin one of the branches, a resistance-coil in the other branch, and asource of current in one of the branches, the polarity of saidlast-mentioned source of current being adapted to oppose the passage ofthe signaling-current through the lamp and its electromotive force beingsuiiicient to prevent the illumination of the lamp by current in thesignaling-circuit, substantially as described.

3. The combination with a telephone-line, of a branch thereof includinga signal-lamp and a source of current, a spring-jack connected with theline, a plug-circuit for making connection with the spring-jack, and aconductor of low resistance connected with the plug adapted to form abridge of the linecircuit including the said source of signalingcurrent,when connection is made with the line, whereby the signal-lamp isshunted.

4. The combination with a telephone-line, of a spring-j ack constitutinga terminal thereof, a signal-lamp together with a source ofsignaling-current in a permanently-closed bridge of the line-circuit, aconnecting-plug and its plug-circuit, and a conductor of low resistanceincluding a signal-lamp connected with the plug adapted to be broughtinto a bridge of the line-circuit when the plug is inserted into thespring-jack, substantially as described.

5. The combination with a telephone-line, of a switch for interruptingthe line at the substation, a spring-j ack constituting a terminal ofthe line in a switchboard, a signal-lamp, a low-resistance branch of theline-circuit including a source of signaling-current temvisorysignal-lamp in said low-resistance" branch, a shunt-circuit including aresistancecoil about the lamp, and a source of current in the closedcircuit formed by the shunt and the conductor including the lamp, thesource of current being so adj usted with relation to the source ofsignaling-current as to produce a condition of no difference ofpotential between the terminals of the supervisory signal when theline-circuit is closed, substantially as described.

6. The combination with a telephone-line, of a switch at the substationfor interrupting the line, a spring-jack for the line in aV switchboard,an impedance-coil, asignal-lamp, and a source of signaling-current in apermanently-closed bridge of the line-circuit, a pair of loop-connecting plugs for uniting lines, the different contact-pieces of each plugbeing united through ahelix or helices of the same induction-coil andthrough a source of signaling-current, a supervisory lamp-signal in theconductor uniting the contact-pieces of each plug, a shunt including aresistance-coil about each supervisory signal-lamp, and a source ofcurrent in each shunt adapted to divert the current of said source ofsignalingcurrent from the corresponding supervisory signal When theline-circuit is closed, substantially as described.

7. The combination with a telephone-line having a switch forinterrupting the line-circuit, a spring-jack for making connection withthe line, of a plug in the spring-jack in continuation of the line, asource-of signalingcurrent in circuit with the plug, the circuit of theplug being divided at one point into two parallel branches, asignal-lamp in one of the branches, and a source of current in one ofthe branches, the said last-mentioned source of current being of suchstrength and polarity as to prevent the illumination of the signallampby current from the signaling-battery, substantially as described.

In witness whereof I hereunto subscribe my name this 29th day of April,A. D. 1895.

CHARLES E. SORIBNER. lVitnesses:

ELLA EDLER, DUNCAN E. WILLETT.

porarily associated with the circuit, a super- IOO IIO

